Seasonal influence on suitability of masquerade tree as a bioindicator of vehicular pollution along university of Ilorin road, Nigeria

This study focused on the seasonal impacts on the suitability of masquerade (Polyalthia longifolia) as a bioindicator of vehicular pollutants. Some leaves of the tree were plucked along the roadside and from a control site with no vehicular emissions. Biochemical parameters, including pH, ascorbic acid content, relative water content, total chlorophyll and air pollution tolerance index (APTI), were determined in both dry and wet seasons using standard methods. Potentially toxic elements (PTEs) commonly associated with automobile pollutants (Pb, Zn, Cr, Mn, Fe and Cu) were analyzed using atomic absorption spectroscopy, after acid digestion. The concentrations of PTEs were slightly higher in leaves from roadside masquerade tree than in those from the control site, except for Cr and Cu at some sampling points during the wet season. The biochemical properties in the roadside samples indicated the presence of pollutants compared to the control site in both seasons. APTI of the roadside samples showed higher sensitivity (mean value = 10.30) in the dry season, indicating a gradual loss in tolerance to pollution; however, a slight increase (mean value = 11.23) in tolerance was observed in the wet season. The masquerade tree demonstrated its sensitivity to vehicular pollution in both seasons. It is more sensitive in the dry season but tends to tolerate pollutants in the wet season by increasing APTI through improved defense mechanisms.